The pictures came from a hardline Sunni group opposed to coalition forces, which has in the past been accused of having links with al-Qaeda.

Our correspondent says the BBC was not given the footage but had to dig it out, adding that the group was not interested in Western news organisations and may have intended the pictures to go to al-Qaeda sympathisers abroad.

It has been cross-checked with other images taken at the time of events and is believed to be genuine. The US does not appear to be questioning its authenticity, our correspondent says.

Ethical training

Amid continuing disquiet about the earlier Haditha claims, the Washington Post on Friday reported that experts with the Naval Criminal Investigative Service (NCIS) hoped to exhume the bodies of several victims in search of evidence.

US marines are suspected of carrying out a massacre and then covering it up.

The US says it is still investigating what happened at Haditha

The forensic evidence was disregarded at first because the November deaths were reported as caused by a roadside bomb and not treated as crimes.

In the wake of the Haditha allegations, the US army on Thursday announced that coalition troops in Iraq were to have training on ethics. The BBC's Ian Pannell in Baghdad says the move is likely to be greeted with cynicism by many Iraqis, as the troops have long been accused of deliberately targeting civilians.

On Friday, the brother of a pregnant woman who says she was shot dead at a US checkpoint in Iraq told the AFP news agency that he would file a complaint against US forces.

The pregnant woman and a relative were shot dead by US forces as they rushed to hospital along a closed road, police and relatives say.

US forces said their car "entered a clearly marked prohibited area near coalition troops" in Samarra and failed to heed warnings to stop.

The brother, who was driving the car and was injured, said he had not seen or heard any warnings.